1. Field of the Invention
The present invention relates to a rear suspension mechanism for a motorcycle.
2. Description of the Prior Art
A rear suspension mechanism for a motorcycle according to the prior art is a type called "full floater type". This full floater type suspension mechanism is an improvement over a type, in which a cushion unit is directly connected either on a middle point of a swing arm having one end hinged to the vicinity of the center of the body and the other end to a rear axle, or on the rear axle. The full floater type suspension mechanism thus improved is schematically shown in FIG. 11 as prior art, in which the aforementioned cushion unit 26 has its one end connected to one end of a bell crank 25 made rotatable on its hinged point at the body and having its other end connected to the aforementioned swing arm 23 through a suitable cushion rod 24. The advantage obtained from that construction is that the ratio of a load upon the rear axle to the repulsive force of the cushion unit, i.e., the so-called "lever ratio" is quadratically changed, as is different from the linear change of the prior art mechanism, with respect to an axle stroke to soften the cushioning performance so that the riding comfort is remarkably improved. The prior art thus far described is well known in the art, as is disclosed in Japanese Patent Application No. 58-45388, for example.
Despite this fact, the conventional full floater type rear suspension mechanism is so constructed that the bell crank has its middle portion hinged to the body, the cushion unit is connected between the one end of that bell crank and the portion of the swing arm, and the other end of the bell crank and the other portion of the swing arm are connected through the cushion rod. As a result, there are left some points still to be improved so as to reduce the weight and size of the suspension mechanism.